VDO Computer Install
 

It's been many, many years since I installed my last bike computer. I remember the installation of my last computer to be a little more involved. With this new VDO C1DS the instructions for mounting the magnet and sensor/transmitter basically just say mount sensor/transmitter to the fork, mount magnet to the spoke, and make sure they close enough to interact. Last time I installed one of these I thought I had to measure and mount at a specific distance from the axle on the fork. Seems like there is something missing in these install instructions.

Trust but verify. Give it a shot and report back on your experience. There may be some adjusting and readjusting required, but their isntructions are basically correct for any sensor/magnet interface.

"Last time I installed one of these I thought I had to measure and mount at a specific distance from the axle on the fork."

Not sure why that would be, the sensor is just counting how many times the magnet goes by per unit of time. There may have been instructions regarding how far away the magnet could be from the sensor and still work.

The one thing you need to be aware of is that the magnet, like all magnets, has two poles and you do not want to mount it so that both poles get counted by the sensor; this will give you double the speed and distance readings. you can use another magnet or a compass to determine just where the poles are; make sure one is close to and one is far from the sensor.

Bring it by and we will have a look.

I suppose the distance from the axle recommendation could be to not to mount the magnet and pickup too far out toward the rim. Obviously the "count" remains unchanged (once per revolution) but the linear speed the magnet passes the pickup goes up as you move it outward. At some point the magnetic pulse may go by too quickly for the pickup to notice it. I've heard various reports on this. Some cyclometers have no problem with mounting the magnet/pickup way outboard and some do.

You guys are right, it shouldn't matter. Once I program the wheel size into the computer the magnet is just counting revolutions. Not sure what I was thinking this morning.

I've never had this problem with any wheel magnet but, I guess if you mounted it "sideways" (i.e. with the flat face of the magnet at 90° to the frame), the pickup could see both poles as separate pulses.

Edit: A couple of magnet ideas:

If you want to mess with your riding buddy, sneak a second magnet on his wheel, 180° away from the first. It's unlikely to be noticed at first but he will be astounded by his new-found speed. :)

I've seen the two magnet idea used intentionally on a reproduction high wheel bike by a rider who wanted to know his distance and speed. The front wheel was so large the cyclometer calibration numbers didn't go that high. He mounted two magnets and used a calibration number 1/2 of the true wheel circumference.

I find with my computers I need to mount the magnet so it passes near the bottom of the sensor. I like to swivel the sensor on the fork blade so it just nearly touches the magnet. I get best results that way. Also make sure the sensor is attached to the front of the fork blade (pointing forward) so it can't get caught in your spokes or bump into the magnet in a way that would damage something.

Robert

All of the wired Cat-Eyes I use have an index line molded into the pickup about 1/4" from the bottom. The instructions say to mount the magnet so the center of the magnet is aligned with that index and with about a 3 mm gap between them.

koolerb, I have a similar C2 DS and I had to trial and error mounting positions. Closer to the hub, about two inches from the flange, with the magnet passing through the lower half of the sensor works best. YMMV

Brad